With the development of information and communications technology, semiconductor technology, and the like, mobile terminals have rapidly been popularized and are being widely used. The mobile terminals provide various functions such as a call function, a music playback function, a message transmission/reception function, a digital broadcast receiving function, an Internet access function, etc.
Meanwhile, batteries are used in mobile terminals for portability. Therefore, due to the usage of batteries, a method for reducing voltage consumption is an important issue in the field of mobile terminals. To reduce the voltage consumption, a mobile terminal is operated in a low-power mode, i.e., a sleep mode, when the mobile terminal is not used. When a wake-up signal is input to the mobile terminal operating in the sleep mode, the sleep mode is disabled, and the terminal is operated in an activation mode in which the terminal is activated.
To switch a terminal from the sleep mode to the wake-up mode or from the wake-up mode to the sleep mode, a key (or button), which is operated by a physically applied force, is provided to a body of the terminal, and the switching is performed in response to a user's operation of pressing the key.
However, in the case where the switching between the sleep mode and the wake-up mode is repeatedly performed by pressing a key exposed to the outside, a defect or failure of the key frequently occurs. Accordingly, recently considered is a method of switching a terminal to the sleep mode or the wake-up mode through a motion, a voice, or the like without physically applying pressure or a contact. However, in the case of such a non-contact method, incorrect operation frequently occurs due to external factors regardless of a user's intention.